Southeastern peninsula of Papua New Guinea

The Southeastern Papuan Rain Forests [AA0120]-dominated by the Owen Stanley highlands, the major mountain range in the ecoregion-contain vast tracts of pristine montane forests (Miller et al. 1994). Because of the dissected landscape and edaphic variations, the ecoregion is rich in endemic species with very local distributions. Although some of PNG's major population centers, including the capital, Port Moresby, are located in this ecoregion, major wilderness areas are still present. This ecoregion is extremely rich because of the diversity of its habitats: it includes coastal, lowland, and montane habitats

Scientific Code

(AA0120)

Ecoregion Category

Australasia

Size

29,900 square miles

Status

Relatively Stable/Intact

Habitats

Description Location and General DescriptionThis lowland and montane ecoregion is made up of the Owen Stanley Range and surrounding lowland and coastal areas in southeastern PNG. The climate of the ecoregion is tropical wet, which is characteristic of this part of Melanesia, located in the western Pacific Ocean north of Australia (National Geographic Society 1999). The surface geology of the Central Cordillera, of which the Owen Stanleys are an extension, is generally composed of metamorphic and intrusive igneous rocks. More specifically, this ecoregion is composed of metamorphosed Mesozoic greywacke sandstone, siltstone, and marine volcanics overlain by Miocene intrusives, Pliocene marine and terrestrial fine-grained sediments, and Quaternary lavas and pyroclastics (Bleeker 1983).

Lowland forest up to 1,400 m on the north side of the Owen Stanleys is made up of Pometia, Terminalia, Myristica, Horsfieldia, Celtis, and Ficus (MacKinnon 1997). Lowland forest is made up of both alluvial and hill types (Paijmans 1975). Lowland alluvial forest has a canopy that is multitiered and irregular, with many emergents. The forest understory contains a shrub-and-herb layer with a variety of climbers, epiphytes, and ferns (Petocz 1989). Palms may be common in the shrub layer (Paijmans 1975). The somewhat lower-canopy, more closed lowland hill forest contains more open shrub layer but a denser herbaceous layer. Palms are fewer in number. The dominant canopy trees include species of Pometia, Canarium, Anisoptera, Cryptocarya, Terminalia, Syzygium, Ficus, Celtis, Dysoxylum, and Buchanania. Koompassia, Dillenia, Eucalyptopsis, Vatica, and Hopea are locally abundant. Dense stands of Araucaria, the tallest tropical trees in the world, are present in scattered locations (Paijmans 1975; Nightingale 1992).

Although they are subject to variable climates and topography, montane forests are smaller crowned and have more even canopies than lowland hill forest. Tree densities can be high, and the shrub density is also high (Paijmans 1975). Lower montane forest transitioning in from the lowlands is dominated by oaks such as Castanopsis acuminatissima, Lithocarpus, elaeocarps, and laurels. Seventy-meter Araucaria may form thick stands in lower areas. Nothofagus, sometimes in monotypic stands, is conspicuous in the moss-covered mid and upper zones of the ecoregion (Davis et al. 1995).

Biodiversity FeaturesOverall richness is generally high and endemism is generally moderate to high when compared with those of other ecoregions in Indo-Malaysia. Bird richness and reptile and amphibian richness and endemism are particularly high in this ecoregion.

The mammalian fauna consists of a wide variety of tropical Australasian marsupials, including tree kangaroos (Flannery 1995). There are 138 mammal species in the ecoregion, of which 28 are endemic or near endemic (Flannery 1995; Flannery and Groves 1998; Bonaccorso et al., in press) (table 1). Included are the critically endangered large-eared nyctophilus (Pharotis imogene) and long-footed hydromine (Leptomys elegans) and Van Deusen's rat (Stenomys vandeuseni) (IUCN 2000; Flannery 1995).

An asterisk signifies that the species' range is limited to this ecoregion.

The avifauna of the ecoregion has a clear Australasian flavor, including representatives of several Australasian families such as Ptilonorhynchidae, Eopsaltriidae, Meliphagidae, and Paradisaeidae. Because the ecoregion includes coastal, lowland, and montane areas, the number of birds found in the ecoregion is quite large (510 bird species). Forty of these are endemic or near endemic (table 2). This ecoregion constitutes the eastern end of the Central Papuan mountains EBA. Whereas the EBA contains a total of fifty-three restricted-range birds, this ecoregion contains only some of them, twenty-seven of which are shared with the Central Ranges montane rain forests ecoregion, one of which is also found in the Central Ranges sub-alpine grasslands, and two of which are found nowhere else on Earth: the streaked bowerbird (Amblyornis subalaris) and eastern parotia (Parotia helenae) (Stattersfield et al. 1998; Beehler et al. 1986; Coates 1985).

An asterisk signifies that the species' range is limited to this ecoregion.

Within this ecoregion, the Kodama Range, with eight endemic species; the Western Owen Stanley Range, with seven endemic species; the Central Owen Stanley Range, with five endemic species; and the Southeastern Coastal area, with one endemic species, are all centers of butterfly endemicity on the island of New Guinea (Parsons 1999).

There are seven recognized Centres of Plant Diversity located in this ecoregion, some of which are shared with the higher Central Ranges sub-alpine grasslands ecoregion. The Galley Reach CPD contains mangrove, lowland swamp, and Nypa communities. Galley Reach contains most of the mangrove species in Papuasia, which in turn has the most mangrove diversity. The Menyamya-Aseki-Amungwiwa-Bowutu Mountains-Lasanga Island CPD ranges from sea level to 3,278 m and represents the diversity of the altitudinal gradient on the north side of the Owen Stanley Range. Lowland rain forests (with extensive dipterocarp forest), lowland swamp forests, lower to upper montane forests, and sub-alpine forests are all represented here. Ultramafic vegetation is found in the Bowutu Mountains. Important lowland forest and ultramafic substrate endemics are found in the Milne Bay-Collinwood Bay to southern coast CPD. The Owen Stanley Mountains CPD contains many local endemics and is the center of diversity for Agapetes (Ericacae). The Varirata and Astrolabe ranges, Safia Savanna, and Topographer's Range CPDs are all little-known areas that merit further study (Davis et al. 1995).

The lowland forests are home to the world's largest butterfly, Ornithoptera alexandrae, a globally threatened species (Miller et al. 1994).

Current Status The East Peninsula Highlands and the North Peninsula Highlands constitute major wilderness areas (Beehler 1994). Five protected areas make up only about 6 percent of the ecoregion area (table 3). Two of the protected areas, Mts. Albert Edward/Victoria and Morobe, are large, more than 1,000 km2 in size (MacKinnon 1997).

Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.

Types and Severity of ThreatsAlthough the threats to this ecoregion are low, potential threats include logging, nickel exploitation, and traditional agriculture (Johns 1993). The extension of the highway from the capital, Port Moresby, through to Milne Bay will increase accessibility of the coastal plain south of the Owen Stanley Ranges, opening this extensive forest area to exploitation (Beehler 1994).

Justification of Ecoregion DelineationUsing Whitmore's (1984) map of the vegetation of Malesia and MacKinnon's (1997) reconstruction of the original vegetation, we delineated the large areas of distinct habitat types as ecoregions. The montane evergreen moist forests along the Central Cordillera, including the Snow Mountains, Star Mountains, Central Highlands, and Eastern Highlands, were placed in the Central Range Montane Rain Forests [AA0105]. This ecoregion roughly corresponds to MacKinnon's subunits P3g, P3h, and P3i. The moist forests in the southeastern peninsula were distinguished as the Southeastern Papuan Rain Forests [AA0120]. This ecoregion consists mostly of montane forests but also includes some lowland forests along the coasts and is roughly equivalent to MacKinnon's (1997) biounit P3n. We used the 1,000-m contour from a DEM (USGS 1996) to define the montane-lowland transition. All along the Central Cordillera and in the Huon Peninsula, we separated the alpine habitat into a distinct-Central Range Sub-Alpine Grasslands [AA1002]-ecoregion. Udvardy (1975) placed these ecoregions in the Papuan biogeographic province of the Oceanian Realm.

Referencesferences for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.Indo-Pacific Reference List

Prepared by: John MorrisonReviewed by:

This text was originally published in the book Terrestrial ecoregions of the Indo-Pacific: a conservation assessment from Island Press. This assessment offers an in-depth analysis of the biodiversity and conservation status of the Indo-Pacific's ecoregions.